Even Spirit Airlines, widely regarded as the nation's cheapest, no-frills flying experience, came in at number 25 among the world's cheapest airlines, according to an analysis of average route prices by WhichAirline.com. Factor in a piece of checked luggage and the airline drops to number 27.

And Southwest, also famous for low-cost flights and no checked bag fee, comes in at number 30 based on average route price only.

The cheapest airline in the world is likely one you've never heard of. It's Firefly, a subsidiary of Malaysia Airlines that flies domestic and international flights to Indonesia, Thailand and Singapore. Potential patrons be forewarned: they do charge for on-board beverages.

The website ranked the airlines by average ticket price based on one-way flights. The average prices were calculated from more than 3,220,000 prices of flights operated in the future (June 2014 and later) searched by WhichAirline.com users.

VivaAerobus, a Mexican low-cost carrier, came in as the second-cheapest airline. AirAsia (Malaysia), SpiceJet (India) and FastJet (South Africa) came in third through fifth places, respectively.

In Europe, Istanbul-based Pegasus Airlines Squeezed out Ryanair for the top spot.